It is known to use solvating polymers for the production of ionically conducting materials. Ethylene oxide or dioxolane polymers are solvating polymers with respect to cations, in particular alkaline metal cations such as for example the Li+ ion present in rechargeable electrochemical generators of the polymer-electrolyte lithium battery type. The semicrystalline character of the polymers has the consequence of reducing the conductivity of the materials that contain them. The crystallinity of the semicrystalline polymers has been reduced by introducing irregularities into the macromolecular chain, without affecting the solvating properties and the electrochemical stability of the copolymer thus obtained. However, it has been found that introducing irregularities into the polyether chain was frequently accompanied by a reduction in the molar masses relative to the ethylene oxide homopolymer and in the mechanical properties, especially at high temperature. It has been sought to remedy this drawback by introducing into the polymer units that allow the formation of three-dimensional networks by crosslinking the copolymer, after it has been formed. Introducing such units into a copolymer has also allowed various groups, and especially ionic groups, to be attached to the macromolecular chain. For example, EP 0 603 370 discloses copolymers comprising repeat units coming from an oxirane and from a dioxolane and optionally bearing groups allowing crosslinking with a third monomer, the example of a third monomer cited comprising a fluorinated segment between a polymerizable group and an ionic group; the crosslinked material then comprises ionic groups connected to a main chain via fluorinated segments. EP 0 657 484 discloses a copolymer comprising a lateral substituent of the alkyl(perfluoroalkyl)sulfonate ether type, for example —CH2—O—(CF2)p—SO3Li. EP 0 671 386 discloses perfluorinated disulfonate monomers and polymers obtained from these monomers, in which the chain-end groups are sulfonates. In both cases, the electrolytes containing said polymers have a cationic transport number t+ substantially equal to 1. However, the incorporation of the fluorinated unit involves synthesis of a very expensive monomer, which is not entirely consumed during the polymerization. This is because the perfluorosulfonate-type ionic functional group is attached to the main polyether chain. Such polymers may be obtained:                by preparation of an oxirane bearing a perfluorosulfonate anion and copolymerization of said oxirane with ethylene oxide or propylene oxide;        by preparation of a compound having at least one C═C double bond, in which one of the carbon atoms bears a perfluorosulfonate anionic group, and by incorporation of said compound by crosslinking to a polyether bearing C═C double bonds.        